Resize a virtual disk

If an existing disk image requires additional space, you can use the qemu-img resize utility to change the size of the image to fit your use case.

Before you begin

  • You have created a backup of the disk image.
  • Any virtual machines (VMs) that use the disk image must be shut down. Warning

    Resizing the disk image of a running VM can cause data corruption or other issues.

  • The hard disk of the host has sufficient free space for the intended disk image size.
  • Optional: You have ensured that the disk image does not have data corruption or similar problems. For instructions, see Checking the consistency of a virtual disk.

Procedure

  1. Determine the location of the disk image file for the VM you want to resize. For example: 
    # virsh domblklist <vm-name>
     
     Target   Source
----------------------------------------------------------
 vda      /home/username/disk-images/example-image.qcow2
  2. Optional: Back up the current disk image. 
    # cp <example-image.qcow2><example-image-backup.qcow2>
  3. Use the qemu-img resize utility to resize the image.

    For example, to increase the <example-image.qcow2> size by 10 gigabytes:

    # qemu-img resize <example-image.qcow2> +10G
  4. Resize the file system, partitions, or physical volumes inside the disk image to use the additional space. To do so in a RHEL guest operating system, use the instructions in Managing storage devices and Managing file systems.

Results

  1. Display information about the resized image and see if it has the intended size: 
    # qemu-img info <converted-image.qcow2>
     
    image: converted-image.qcow2
file format: qcow2
virtual size: 30 GiB (32212254720 bytes)
disk size: 196 KiB
cluster_size: 65536
Format specific information:
    compat: 1.1
    compression type: zlib
    lazy refcounts: false
    refcount bits: 16
    corrupt: false
    extended l2: false
  2. Check the resized disk image for potential errors. For instructions, see Checking the consistency of a virtual disk.